Ring communications involving data transmission is well-known. One such loop transmission scheme is shown in the specification of U.S. Pat. No. 4,064,486.
These rings or loops are used to transmit data in the form of binary encoded signals over relatively large distances.
In most commonly used rings or loops, provision is made for physically interconnecting and removing stations, as well as placing the communication paths through or over physical obstacles.
In use, the data ring may experience a break somewhere in a widely dispersed network. For example, the network may be placed between buildings or between separate levels in a building, or through cable ways making examination of each separate piece of cable difficult and expensive, as well as time consuming. Accordingly, past devices have not had a fast easy method or apparatus for identifying the location of the cable fault or at least localizing it so that repairs can be quickly directed to the location of the damaged cable, effecting rapid reestablishment of the data network.
In most ring communication networks, each station's timing clock is derived from the ring data rate. Decoders separate the timing signal and the data signals from the ring loop data and then use the timing signals to synchronize the station clock.
Additionally, and as in most rings, a match of a station address with an incoming information packet destination address is required before the data is extracted from a packet.
In past systems, data defining the address of the station was loaded in parallel to a station register and then that stored address was compared bit by bit with an incoming destination address in a packet.